Radio receiver



June 18, 1940. J. SCHWAEN 2,205,365

RADIO RECEIVER Filed July 18, 1938 Fig.1

INVENTOR J. L .SCHWAEN BY Q4- ATTORNEY Patented June 18, 1940 UNITED STATES ATENT pol-"rice John Louis Schwaen, Tampa, Fla., assignor of one-half to Marguerite Schwaen, Tampa, Fla.

Application July 18, 1938, Serial No. 219,791

6 Cllaims. (Cl. 250-20) An object of this invention is to provide a novel radio receiver in which an undesirable component, such as disturbances due to static, may be balanced out and the desired signal may be received and heard free of such disturbances.

A further object is to provide a receiver in which the undesirable component is eliminated at the portion of the receiver where the energy of the signal currents is converted into the energy of sound waves.

A still further object is to provide a sound translating device, such asa loudspeaker, with two or more coil windings which are not connected together but each. is connected to a separate radio receiver or to a separate part of a combined radio receiver having two or more tuning units.

Other and further objects of't'he invention will become apparent :to those skilled in the art as the description thereof proceeds. For a better understanding of the invention reference is made to the accompanying drawing, in which:

Fig. 1 is a circuit diagram of a radio receiver embodying the invention and showing in section a portion of the loud speaker, and,

Fig. 2 is a circuit diagram of a radio receiver having three tuning units and embodying the invention.

Referring to Fig. 1, the antenna circuit 52 comprises primary windings lo and H which are coupled to the resonant input circuits 1 and 8 of radio receivers R and R. Circuit i may be tuned by condenser 'l to a desired carrier frequency of, for example, 1100 kilocycles and its constants such that it passes the carrier and both side bands to the amplifier tube of the tuner. This condition I refer to by the term broadly tuned. Resonant input circuit 8 of receiver R may be tuned to a frequency slightly above or below the carrier frequency and its constants are so chosen that it is more selective than circuit I so that it does not transmit the side band frequencies. When the modulation frequency has a range from 0 up to 6,000 cycles, circuit 8 may, for example, be resonant at a frequency of 1095 or 1105 kilocycles. The output terminals !3 of amplifier tuner T are connected to the input terminals M of a vacuum tube detector D whose output terminals l5 are in turn connected to the input terminals iii of an audio frequency amplifier A. The output terminals ll of A are coupled by a transformer 2 and leads 22 to the multiple turn winding 3 of a sound reproducer S represented diagrammatically as an electrodynamic loud speaker. Coil 3 is Wound on a cylindrical coil form l8 attached to'the small end of the cone 4 of the speaker, the opposed pole pieces 25 and 26 of field magnet 24 being adjacent form l8. Radio receiver R is otherwise similar to receiver R and its parts are marked with similar letters primed. Its output terminals ll are coupled by transformer 6 and leads 23 to a coil winding 5 shown as wound in the opposite direction to winding 3. his, however, is not necessary as the coils may be wound in the same direction and their connections to transformers 2 and t reversed. The essential requirement isthat the currents through the two windings at any instant shall produce magnetic fields which are in opposite directions.

It is preferable that there be no tension tend ing to move the cone diaphragm 4 either to the left or right and I have shown it asa free float ing diaphragm supported from a fixed frame l9 by the annular rings of thin chamcis 20 and 52! whose inner edges are cemented to the cone and whose outer peripheries are cemented to frame IS in the positions shown. It will be understood that with the construction shown, the modulation frequency current and undesired current components representing static or interfering electrical. fields located between the transmitter and receiver, will pass through coil 3 and cause diaphragm 4 to reproduce the signal. However, currents of the undesired frequency passing through coils 3 and 5, tend to move the cone diaphragm in opposite directions and hence their effects are neutralized and the none of the static is eliminated. It will be noted thatthe interference is balanced out at that portion of the receiver where the electrical energy is converted intomech'anical energy. I have also found that the inertia of the r speaker diaphragm absorbs a large percentage of any unbalance which may be present due to operating the device with a greater percentage of tolerance than possible when trying to balance out the interference in any other part of the circuit. It will also be understood that a loud speaker is not necessary but that the opposed windings 3 and 5 may be employed for the windings of a headphone receiver. .It will also be understood that magnet 24 may have a field coil or be of the permanent type and that coils 3 and 5 need not have the same number of turns. This will depend on the magnitude of the current strength flowing through them and it is possible by a greater number of turns to compensate for a smaller current in one winding the effect of a larger current in the other.

A second embodiment of the invention is shown in Fig. 2 in which receivers R, R and R" are similar to those shown in connection with Fig. 1 except as to the tuning of their input circuits. In this case circuit I may be tuned to the carrier frequency, circuit 8 to a frequency slightly higher than the carrier frequency and circuit 29 tuned to a frequency slightly lower than the carrier frequency by condenser 30. Circuit l is broadly tuned so as to pass a wide band of frequencies including both side bands while circuits 8 and 29 are sharply tuned or have a high selectivity so as not to pass a wide band of modulation frequencies. In this case the voice coil form has a third winding 27 in addition to the windings 3 and 5, windingZl being connected to the output transformer 28 of receiver R" by leads 3|. In this case it Will be understood that the voice coil windings 3, 5 and 21 are wound or connected in such directions that the static or undesired component of currents passing through them tend to move the speaker in opposite directions and the static or undesired signal component is balanced out while the useful signal component (modulation frequency) is available in coil 3 to reproduce the desired signal,

While I have shown two embodiments of my invention, it will be understood that it is by no means limited to the embodiment shown but embraces all receiver arrangements and constructions coming within the scope of the annexed claims.

What I claim is:

1. In a signalling system having desired currents and undesired components, the combination of a sound reproducer having a steady magnetic field, a diaphragm, at least two coils mechanically connected to said diaphragm and each having a plurality of turns located in said field, means including an audio frequency transformer for supplying the desired currents to only one of said coils and means including a second audio frequency transformer unconnected to said first transformer whereby currents having the undesired components are supplied to both of said coils in opposed phase relation whereby said diaphragm generates sound waves of a frequency equal to that of the desired currents only.

2. In a signalling system, the combination of a receiver having an input circuit broadly tuned to pass a carrier and its side band frequencies, a sound reproducer having a diaphragm mounted to vibrate as a piston, at least two coils mechanically connected to said diaphragm and insulated from each other and unconnected together, means for creating a magnetic field about said coils, means coupling the output terminals of said receiver to one of said coils, a second receiver having an input circuit of greater selectivity than said first input circuit and tuned to a radio frequency somewhat higher than the carrier frequency and having an admittance band such as to reject the side band frequencies, and means coupling the output terminals of said second receiver to the other of said coils.

3. The combination of claim 2 in which said diaphragm is suspended for free movement and has sufficient inertia to prevent its motion by slightly unbalanced currents in said coils and in which the electromagnetic field of one of said coils is substantially 180 degrees out of phase with the field of the other coil.

4. In a signalling system the combination of a radio frequency amplifier having an input circuit broadly. tuned to transmit a carrier and its side band frequencies, a detector having input terminals connected to the output terminals of said amplifier, a sound reproducer having a diaphragm supported for free vibration, two coils mechanically connected to said diaphragm and unconnected to each other, means for generating a steady magnetic field about said coils, means coupling the output terminals of said detector to one of said coils, a second radio frequency amplifier having an input circuit sharply tuned and having an admittance band such as to reject the side band frequencies, a second detector having its input terminals coupled to the output terminals of said second amplifier, and means coupling the output terminals of said second detector to the other of said coils, the direction of winding of said coils being such that their electromagnetic fields are substantially 180 degrees out of phase.

5. In a signalling system, the combination of a diaphragm supported to vibrate as a piston, means for producing a steady magnetic field, three coils electrically unconnected with each other located in said field andmechanically connected to said diaphragm, means for supplying currents of undesired components only to two of said coils, means for supplying currents of undesired components and currents of a desired signal frequency to the third of said coils, the number of turns and the direction of winding of said coils being so related that the resultant electromagnetic field produced by currents of the undesired components has substantially no effect on the motion of said diaphragm.

6. A signalling system adapted to receive av carrier current modulated by a band of audio frequencies and comprising, the combination of a radio frequency amplifier having a parallel resonant input circuit broadly tuned to a carrier and side band frequencies, a sound reproducer having a diaphragm supported to vibrate as a piston, at least three coils mechanically connected to said diaphragm and electrically unconnected with each other, means for generating a steady magnetic field about said coils, means including a detector coupling the output terminals of said amplifier to one of said coils, a second radio frequency amplifier having an input circuit sharply tuned to a frequency near the upper end of said side band, means including a detector coupling the output terminals of said second amplifier to another of said coils, a third radio frequency amplifier having an input circuit sharply tuned to a frequency near the lower end of said side band, means including a detector coupling the output terminals of said third named amplifier to the third of said coils and a source of radio frequency currents coupled to each of said input circuits.

JOHN LOUIS SCHWAEN. 

